Fluid delivery systems and devices are often used to provide pharmaceuticals to the body of a human or animal subject. Such systems and devices may employ catheters for fluid delivery. It is also known in the art to implant electrodes and electrical prosthesis in the body to provide electrical stimulation to internal organs and tissue.
For example, intra cochlear electrodes are intended to restore some sense of hearing by direct electrical stimulation of the neural tissue in proximity of an electrode contact. As more and more patients with significant and usable residual hearing are implanted with cochlear implants, it becomes imperative to use a minimally traumatic electrode. In addition, devices may be implanted in a subject when the subject is at a very young age and it may be necessary to re-implant several times during a lifetime. Each consecutive insertion of a cochlear implant may cause trauma to spiral ganglion cells to a minimum. Trauma to spiral ganglion cell is cumulative and cannot be undone in the present state of technology.
To reduce trauma to the organ or tissue, electrodes and catheters should be soft, flexible, and insertion forces should be minimum. Unfortunately, most cochlear implant electrodes on the market today require significant force to be inserted, even for distances which are much less than the full length of the scala tympani.
The required force to insert the electrode or catheter is related to the size, geometry, and the material used in the fabrication of the particular device. Material used in such devices includes materials for wires, contacts, functional metallic or polymer segment, and bulk material. The size of the electrode or catheter, the rigidity of the material used in the electrode or catheter, the hydrophobicity of the outer shell of the electrode array, the energy stored in one way or another in the electrode and the insertion process of the device have an impact on the amount and location of damages that will be inflected to the tissue of the labyrinthe during electrode placement. With respect to fluid delivery systems in general, removal and replacement of the system or of particular parts of the system may also cause trauma and damage to living tissue.
Damage and trauma cause bleeding, inflammation, perforation of soft tissue, tears and holes into membranes, and fracture of thin osseous structures. The resulting damage to the inner ear, for example, may cause loss of surviving hair cells, retrograde degeneration of the dendrite which inervates the organ of Corti, and in the worst case, spiral ganglion cell death in the Rosenthal's canal. Cell death means quantitatively less neural tissue is available for stimulation, and qualitatively, that less frequency-tuned fibers are available to represent frequency information. Loss of dendrites without loss of spiral ganglion means that acoustic stimulation is no longer possible, and that no synergetic effects between acoustic and electric stimulation is available. Electro-acoustic synergetic effects may be critical for good sound discrimination in noisy environments.